Sulfide Inclusion-Induced Micro-scaled Pitting Corrosion on Crankshaft Surface in Indoor Atmospheric Environment.

This paper originally investigates the sulfide inclusion-induced micro-scaled pitting corrosion in indoor atmospheric environment on automotive crankshafts manufactured by classical non-quenched and tempered steel using scanning electron microscope using energy-dispersive spectrometer. The crankshafts, which were disassembled from gasoline engines with low mileage after specific tests, were stored in an indoor atmospheric environment with an ambient humidity of approximately 75% for 2 weeks. The experimental results show that the anodic reaction initially took place at the sulfide inclusion/steel matrix interface, which was induced by the sulfide inclusion wherever very small amount of residual neutral chloride medium on the crankshaft surface was activated by moisture in the air. In addition, the reaction products could accelerate the rate of pitting corrosion toward the steel matrix in nearby micro-zones, and tiny rust that could be hardly observed by visual inspection, as a result, appeared in micro-scale on the experimental crankshaft surface even in indoor atmospheric environment. It is concluded that even when the crankshaft is stored indoors, special attention should be pertinently paid to corrosion prevention, for example, to remove all corrosive media on surface carefully by fine cleaning, to implement rust prevention measures, and to control humidity of atmospheric environment at a proper level. [ABSTRACT FROM AUTHOR]